Delay line



M. BJKLINE July 9, 1957 DELAY LINE 2 Sheets-Sheet l Filed Nov. 14. 1952 INVENTOR. MELVIN B. KL/NE 12 y 2 ATTORNEYS July 9, 1957 KLINE 2,799,007

DELAY LINE 1 Filed NOV. 14, 1952 2 Sheets-Sheet 2 INVENTOR. MELVIN B. KL/NE vwww ATTORNEYS United States Patent DELAY LINE Melvin B. Kline, Rutherford, N. J., assignor to Allen B.

Du Mont Laboratories, Inc., Clifton, N. J., a corporation of Delaware I Application November 14, 1952, Serial No. 320,424

3 Claims. (Cl. 333-31) This invention relates to delay lines, and more particularly to a continuously variable delay line, which is of extremely compact design and may be precisely wound and accurately calibrated.

It has long been known that a filter network comprising a series of lumped inductors and capacitors may be used to simulate a transmission line and that the amount of transmission delay desired may be selected by switching from one section to another. This results in the introduction of delay in finite steps, the amount of delay, T, introduced, as well as the characteristic impedance, Z, depending on the value of the inductors, L, and capacitors, C, according to relationship.

It is an object of my invention to provide a continuously variable delay line which may be accurately calibrated and which will retain its calibration over long periods of time.

It is another object of my invention to provide a continuously variable delay line which is extremely compact and may be operated by rotating a single knob.

Other objects will become apparent from a study of the specification and drawings showing typical embodiments of the invention.

My invention contemplates the use of an inductance comprising a Wire helically wound to form a coil which in turn is wound to form a helix. This type of winding has been called a coiled coil, and will be so designated hereinafter. Contact is made to each individual turn by a mechanism, which provides for sliding of the contact continuously from one end to the other as a variable tap.

In the drawings:

Figure 1 is an elevational view of a portion of the conductor showing the manner in which the helically formed coil is wound;

Figure 2 is a perspective view of the coil formed into a helix;

Figure 3 is a view, partly broken away, of one embodiment of the device showing the assembly of the coil and a slider mechanism in a case;

Figure 4 is a view, sectional through the case, of another embodiment of the device, showing a modified assembly of the coil and slider mechanism;

Figures 5 and 6 are sectional views taken along the lines 5-5 and 66 respectively of Figure 4.

Referring now to Figure l, a core 5 in one embodiment of a plastic material such as nylon, has wound thereabout a coil 6 of a conductor such as enameled copper wire. The coil 6 may be close wound as shown in Figure 1 or the turns may be spaced. A close wound coil having contacting adjacent turns should be insulated. Close winding has the advantage of increased inductance and capacitance per unit length.

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coil or'by a metallic stripe or stripes along the length of the core, or spiralled therearound. In the latter case the stripes are coaxial with the coil so as not to form a shorter turn on the core. The entire inside wall of the case may be coated with a layer of conductive foil or paint 13 from which a lead may be brought to the outside of the case.

The insulation is removed from the coil along the side facing inwardly so that a sliding contact 8, which is held against the coil by a spring 9, may contact the individual turns of the coil. The opposite end of the spring is fastened to a slider 10 formed on an enlarged portion 14 of a shaft 12 which may be rotated. This enlarged portion of the shaft is made in the form of a hollow cage which is force fitted on the shaft 12 and may be insulated therefrom. Contact is made to the cage 14 by means of a spring 15. The sides of the slider are elongated so as to form two sides of a shoe which fits over the solenoidal coil 6 and which, by the helical shape of the coil, forces the slider to travel along the channel 11 as the shaft is rotated, thus causing the contact 8 to make contact along the entire length of the coil.

Figure 4 shows another embodiment of the device, in which the coiled coil is secured to a drum 24 free to rotate and the slider 10 is arranged to slide in a guide 11 fastened to the outer housing 17, similar parts bearing the same reference characters as in Figure 3. The spring 9 causes pressure to be exerted on the contact 8 as well as on the pin 25 which makes contact with the guide 11 or to a metallic strip placed in the bottom of the guide. The outer portion of the drum is grooved and the coiled coil is fitted into the grooves. The insulation is then removed from the coil along the side facing outwardly. In this embodiment the entire outer portion of the drum may be coated with a layer of conductive foil or paint 13 which is connected electrically to a contact 23 secured to the rear of the drum and upon which bears a spring contact 16 fastened to the housing with a terminal portion 16a extending through the housing. On both ends of the drum circular slip rings 18 are secured and each end of the coil is electrically connected thereto. Spring biased contacts 19 secured to the ends of springs 20 bear against the slip rings and are fastened to the housing by rivets 21, extensions of these springs extending through the housing and forming terminals 22 from which connections are made to the external circuit.

It will be understood that this device may be used as a fixed delay device by connecting to the terminals connected to the ends of the coil, omitting use of the variable tap feature or by omitting the sliding tap altogether.

While specific embodiments have been described, the invention is defined by the following claims.

What is claimed is:

l. A variable delay line which comprises a generally cylindrical body of electrically insulating material having a helical groove on its outer surface, a coiled coil of insulated high electrical conductivity material mounted in said groove on said body, means for contacting individual turns of said high conductivity material on 3 the outer surface thereof, means for rotating said body about its axis relative to said contacting means and means comprising a coating of conductive material on the outer surface of said body for increasing the ,distributed capacity of said variable line.

2. The device of claim 1 in which said meansfor con-v tacting comprises a slidable contact shoe mounted on a member positioned adjacent said 'body' and arranged to slide in a direction parallel to the axis of said body.

3. A variable delay line which comprises a generally cylindrical body of electrically insulating material 'having a heical groove formed therein, a coiled conductor comprising a plurality of turns of high conductivity material Wound upon and insulated from a base material, said coiled conductor being placed in said groove, a generally cylindrical case surrounding said body, a member mounted in said case, said member carrying a s lidable shoe arranged to contact the individual turns of said coiled conductor, means to rotate said body relative to said member to cause said shoe tomove in ,a direction parallel to the axis of said body thus contacting selec- References Cited the file of this patent UNITED STATES PATENTS 2,12 6,541 De Forest g Aug. 9, 1 938 2,233,748 Rust Mar. 4, 1941 2,399,060 Puerner Apr. 23, 1946 2,416,683 Finch et al Mar. 4, 1947 2,420,559 Nelson May 13, 1947 2,452,572 Iago p Nov. 2, 1948 2,467,857 .Rubel et a1. Apr. 19, 1949 2,599,126 Reed June 3, 1952 2,619,537 Kihn Nov. 25, 1952 FOREIGN PATENTS 121,339 Australia Oct. 2, 1947 

